This invention relates to an apparatus for continuously assessing the flexural strength and stiffness of relatively rigid materials such as wood and particularly materials which have been joined end to end by means of an adhesive.
Laminated wooden beams and arches are typically manufactured from laminates whose cross-sections nominally range from 1".times.4" to 2".times.12" and whose lengths vary up to 165' (limited by manufacturing space). Lumber is trimmed to remove certain defects which are located near the ends so random lengths result. It is possible to use this lumber by cutting end joints and gluing these ends together. Quality control requirements of the AITC (American Institute for Timber Construction) dictate, however, that random end joint samples be tested to a required strength. In addition, further requirements stipulate that no two end joints located in the tension zone of a beam or anywhere in a tension member be stacked within six inches of each other in adjacent laminations in a laminated product because of the potential for a weak end joint that has not been verified by proofloading.
If all end joints could be individually tested and minimum strength established for the joint, the AITC requirements for stacked joints in the tension zone could be waived because the joint would have been proofloaded. In addition, the establishment of a minimum flexural strength for individual joints would assure the manufacturer that in meeting the design specifications he can minimize his risk of product liability.
Not only would mismanufactured end joints be discovered immediately, other natural strength reducing characteristics would be better controlled and also, the variable stiffness along the length of the lamination would be monitored. The system would therefore greatly improve the structural reliability of the end product. Immediate detection of defective end joints has the advantage of being more economical than if they are detected later in the manufacturing process.